Flexible electric surface heater

ABSTRACT

A flexible electric surface heater comprises at least two flexible and heatproof plastic films and an electrically heat generating metal foil formed in a zigzag form between said plastic films through a thermoplastic resin as a filler. An excess heat detecting electrode is embedded also between the plastic films along the zigzag metal foil so as to oppose thereto with a fixed distance through the filler, and is connected to a protective device for interrupting power supply when extraordinary heat is detected at the electrode. The surface heater is continuously manufactured by laminating the metal foil on one of the plastic, forming the zigzag heater line as well as the electrode by means of an etching process, and further laminating another plastic film.

United States Patent Inventors Kazuo Dol;

Ryuzo Kata; Tadashi Matsumoto; Fujio Nilzuma; Shigenori Kugumiya; YasuoTanalta; Motobaru Kitamura, all of Kadoma, Osaka, Japan Appl. No.802,071

Filed Feb. 25, 1969 Patented June 8, 1971 Assignee Matsusbita DenkoKabushiki Kaisha Osaka, Japan Priority Feb. 29, 1968, Feb. 29, 1968,Feb. 29,

1968, Feb. 29, 1968, Feb. 29, 1968, Feb. 29, 1968, Feb. 29, 1968, Feb.29, 1968 Japan 43/1603], 43/19314, 43/31529, 43/45504, 43/25976,43/45516, 43/51520 and 43/58172 FLEXIBLE ELECTRIC SURFACE HEATER 1Claim, 19 Drawing Figs.

US. Cl 219/549, 219/528, 219/544, 338/212 Int. Cl 1105b 3/36 Fleld ofSearch [56] References Cited UNITED STATES PATENTS 2,666,839 l/1954Boctel 2 I 9/528 2,719,213 9/1955 Johnson 338/212 3,031,739 5/1962 Boggs2l9/345X 3,215,574 11/1965 Korb 219/212UX 3,423,574 l/l969 Shomphe eta1. 219/528 Primary Examiner-Harold Broome Attorney-Wolfe, Hubbard,Leydig, Voit and Osann ABSTRACT: A flexible electric surface heatercomprises at least two flexible and heatproof plastic films and anelectrically heat generating metal foil formed in a zigzag form C L-e.v.v

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INVENTORS KAZUO DOI RYuzo Karo TADASHI MArsumoro FUJIO NIIZUMA SHIGENORIKueumnm YASUO TANAKA MOTOHARU KITAMURA ATTORNEYS PATENTEBJM man 3584.198

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A 27 {Jim M M Lfll ik INVENTORS KAzuo Do! Rvuzo KATO TADASHI MATSUMOTOFuaao NIIZUMA SHIGENORI KUGUMIYA YASUO TANAKA Mo-roHARu KITAMURAATTORNEYS FLEXIBLE ELECTRIC SURFACE HEATER This invention-relates tosuch an electric surface heater and a method of manufacturing the same,that fonned in a plane andflexible member, in which an electrically heatgenerating line consisting of a metallic foil is sealed through a fillerbetween plastic films, respective which being flexible and high inheatproofness and electric-insulativeness.

Conventional surface heaters of the kind have been in volved in suchvarious defects that, for example, breaking or disconnecting accidentsof the heat generating line have been easily occurred since anyconsideration of making respective thermal expansion coefficients of theheat generating line and external covering sheet for protecting the linesubstantially equal to each other has been made, and that the heatershave been lacking in safety and difficult to be used or adhered to eachother as bent or folded back since thermostat elements to be assembledin the surface heater have not been of the type that is flexible butrather that having a certain thickness.

The present invention has been suggested to remove such defects as aboveof conventional electric surface heaters.

Thus the principal object of the present invention is to provide anelectric surface heater which is not in danger of causing any linebreaking accidents to occur even though the heat generating line isformed of an extremely thin metal foil.

It is another object of the present invention to provide an electricsurface heater which is high in safety characteristics with a provisionof flexible and thin type safety device that will be actuated inresponse to sensing of any excessive temperature rise, and which furtheris easily treated upon mounting operation with its high flexibility.

It is another object of the present invention to provide a surfaceheater which allows to readily represent thereon decorative pattern ordesign, or any reference symbols.

It is a further object of the present invention to provide an electricsurface heater which is readily adaptable to various usages by varyingheat generating amount per a unit of area at each part of the heater.

Other objects and advantages of the invention will become apparent uponreading the following detailed description and upon reference to theattached drawings in which:

FIG. 1A is a plan view of the electric surface heater according to thepresent invention;

FIG. 1B is a sectioned view taken along the line I-l in FIG. 1A;

FIGS. 2A-2C inclusive are diagrams showing steps of the method ofmanufacturing the electric surface heater according to the presentinvention, respectively;

FIG. 3A is a plan view of another embodiment of the present invention,in whichan insulating film at a surface of the heater is shown as partlyremoved;

FIG. 3B is a sectioned view taken along the line III-III in FIG. 3A;

FIG. 3C is a wiring diagram of the heater under use;

FIG. 4A is a plan view of another embodiment, in which an insulatingfilm 'at a surface of the heater is shown as partly removed;

FIG. 4B is a sectioned view taken along the line IV-IV in FIG. 4A;

FIGS. 4C and 4D show examples of wiring diagram of the heater under use;

FIGS. 5A and 5B are perspective view showing connection of lead wires;

FIGS. 6A and 6B show further embodiments of the inven- 7 tion,respectively;

FIG. 7 shows another embodiment of the invention;

FIG. 8A shows a further embodiment of the invention; and

FIG. 8B shows an insulating method at peripheral edges of the surfaceheater according to the present invention.

While the'invention has been described with reference to certainpreferred embodiments, it will be'understood that it is not intended tolimit the invention to the particular embodiments shown but ratherintended, on the contrary, to cover the various alternatives andequivalent forms of the invention as coveredby the spirit and scope ofthe appended claims.

Turning now to the drawings, there is shown in FIGS. 1A and 15 anembodiment of the invention. In the drawings, 1 and 3 are respectively aplastic film which having a flexibility, heatproofness and highinsulativeness, and 2 is a heat generating member consisting of a metalor an alloy film. The heat generating member 2 is embedded between theabove-mentioned insulating films l and 3 through a filler 4 whichconsists of such a thermoplastic resin as polyethylene, polyamide,polyvinyl formal, polyurethane series adhesives, nitrile rubber or thelike. The member 2 willbe formed in a lattice or. a zigzag form as shownin FIG. 1A.

For said plastic films l and 3, any of such materials as shown in thefollowing Table 1 will be used, respective which having characteristicsas listed therein.

Further, for the said heat generating member 2, any of such materials asin the following Table 2, respective which having characteristics aslisted therein.

As above, such a material for the plastic film 1 and 3 that its thermalexpansion coefficiency lies within the range of 2.0Xl0 C. to 7.0Xl0"'/C. will be selected and also such a material for the heat generatingmember 2 that its thermal expansion coefficiency lies within the rangeof l.0Xl0 C. to 4.0XI0" C. will be selected so that respective thermalexpansion coefficiencies of the both materials will be substantiallyidentical to each other, thereby the breaking or disconnection of theheat generating line resulting from any difference between each of thethermal expansion coefficiencies of the both materials will beeffectively prevented from occurring. That is, the selection of propermaterials for the plastic films l and 3 and for the heat generatingmember 2 within the range of thermal expansion coefficiency asrestricted in the above will enable it possible, in conjunction withcushioning effect of the tiller 4, to prevent the breaking ordisconnection of the heat generating line member.

As for the thickness of the materialsto be used in practice, the plasticfilm material will be selected from the range of 10 to 500p. and theheat generating member material will be selected from the range of 20 top, so that the completed product will be of thickness within the rangeof 100 to 600p.

The method of manufacturing the electric surface heater having theabove-described structure shall now be disclosed.

Referring now to FIGS. 2A to 2C, the plastic film 1 and metallic foil 2are sequentially adhered to each other through a layer 4' of such athermoplastic resin, supplied from an extruder 5 in a melting state, aspolyethylene, vinyl chloride vinyl acetate copolymer, nylon or the like,or a binder of nitryl rubber series, urethane series or the like, undera pressure by means of a sequential laminators 6 so that a laminatedfilm A having a metallic foil will be formed (FIG. 2A). In order toobtain a form of the heat generating line according to the presentinvention from said metallic foil 2 on the laminated film A, ananticorrosive ink against any etching ground material will be thenprinted in the said form on the surface of said foil 2 by means of aphotogravure printing method or a sequential screen printing method. Itwill be understood that this printing step may be effected on themetallic foil 2 prior to the above adhering step of the plastic film 1and metallic foil 2. The laminated film A will then be dipped into sucha corrosive etching ground liquidcontained in an etching tank 7 asferric chloride solution, chromic acid solution, persulfuric acidammonia solution or the like, so that the part of metallic foil 2 notcovered with the anticorrosive ink will be corroded or etched in acontinuous manner, after which the laminated film A will be furtherprocessed through a washing tank 8 and a drying chamber 9 and, thus, theheat generating line will be formed on the plastic film -1 (FIG. 2B).The laminated film A thus etching processed and a further plastic film 3are adhered to each other under a pressure by means of a furtherlaminator 6', through such a thermoplastic resin 4", supplied from anextruder 10 in a melting state, as polyethylene, vinyl chrolide-vinylacetate copolymer, nylon or the like (FIG. 2C).

It is known that usual binders or adhesives which generally containsolvents that not much volatile are inconvenient for being painted in athick layer. Because of this defect, when one of such adhesives is used,the recess on the laminated film A after etching processed will not becompletely filled with the adhesive material and, therefore, the film Aetching processed and plastic film 3 will have to be adhered to eachother with a layer of air remained at certain portions of the recess,which will cause binding force between both films to becomedeteriorated. This will happen even when the adhesive material isapplied to the films in a relatively thin layer. On the other hand, inthe method according to the present invention, due to the fact that athermoplastic resin in a melted condition which is easily painted in athick layer is utilized, the recess formed after the etching processwill be completely filled with the resin. Therefore, the plastic filmhaving the metallic foil now in the form of heat generating line of theinvention will be effectively jointed to the other plastic film withoutcausing any bubbles to be remained between the both plastic films 1 and3 so that their binding force will become excellent.

Further according to the present invention, it is easily possible tostrip off one of the plastic films from the other having the etchedmetallic foil thereto, simply by heating the whole, since athermoplastic resin is utilized for the filler. Therefore, line breakingportion of the metallic foil can be easily exposed by stripping off thesurface plastic film at the time of such disconnection trouble and,after connecting work is established, the stripped off plastic film maybe adhered again to the otherfilm so as to cover the line by means of aheat sealing, so that the heater will be again able to be used.

An example of the manufacturing method shall be explained next.

A polyester film of 75p. thick rolled in a coil form and an aluminumfoil of 20p. thick rolled in a coil form are set in a feed device of thelaminator. After giving an anchor coating to the polyester film, heatedpolyethylene up to 300 C. is made to fall down from an extruder onto thefilm so as to be 40p. thick right before the aluminum foil is applied tothe film. The foil and film are pressed by means of nip rollers so as tobe adhered to each other with the polyester, and then are rolled up inthe form of laminated film. An anticorrosive ink will then be printed onthe side of aluminum foil of the above laminated film, in apredetermined shape for the heat generating line and a layer of 25p.thick, by means of the photogravure method. The laminated film thusprinted will be processed through the ferric chloride solution tank,washing tank and drying chamber in a sequential manner. Leaving theanticorrosive ink on the foil as printed, said laminated film and afurther polyester film of 25p. thick are supplied to a further laminatorwith the etched surface of laminated film inside, while a furtherpolyethylene is inserted between them so as to be in a layer of 40 4.thick with the above mention manner, so that the latter polyethylenelayer will be fused to the polyethylene applied to the first polyesterfilm at the former step through recessed or lost part of the aluminumfoil after the etching process. Through these steps and processes, asurface heater having a high flexibility has been obtained.

Turning now to FIGS. 3A, 3B and 3C,'another embodiment of the presentinvention shall now be referred to.

This embodiment is to provide a-surface heater provided with aprotective device therein for enabling the heater to sense any excessiveheat by itself in the case when the surface heater generates suchexcessive heat due to any causes, so that any fire accident will beprotected from occurring.

ln FIGS. 3A and 3B, 1 is a heatproof plastic film of, for example,saturated polyester resin, and 2 is a conductor laminated on saidplastic film l for actuating as a heat generating member, which will bearranged in a lattice or zigzag form. 11 is a plurality of electrodeplate, which will be respectively positioned between each turn of saidconductor with a fixed space a from the conductor. Said electrode plates11 are interconnected at peripheral part of the plastic film 1 by meansof a lead wire 12. 13 is a filler of such thermosensitive organicmaterial having a negative temperature resistive coefficiency as, forexample, polyamide, polyvinyl formal or the like, and the filler 13 isfilled in the space between the heat generating member 2 and respectiveelectrode plates 11. 3 is a further heatproof plastic film coveringupper surface of the heat generating member 2, electrodes 11 and filler13.

The thermosensitive surface heater having the structure as above will beformed, as will be apparent from the foregoing, by adhering an aluminumfoil to upper surface of the heatproof and insulative plastic film whichis flexible and consists of, for example, saturated polyester film,printing respective forms of the heat generating member and electrodesincluding the lead wire for the latter on the said foil with ananticorro-.

sive ink, effecting the etching process with a corrosive etching groundsolution so that the heat generating member 2 and electrode plates 11interconnected by the lead will be formed on the heatproof andinsulative film 1 all with the-same metal material in a plane surfacestructure, filling the thermosensitive organic material into spacesbetween the heat generating member 2 and respective electrode plates 11,and then covering the upper surface of the above structure with afurther heatproof and insulative plastic film l Thus formedthermosensitive electric surface heater will be used in the followingmanner.

As shown in FIG. 3C, both of initial and tail ends of the heatgenerating conductor member 2 will be connected through a switch 14 torespective terminals of a power source 15, and a protecting device 16 isinterconnected between the lead wire 12 for the electrodes 11 and a leadwire 17 from the member 2 to the switch 14. The arrangement is suchthat, when an extraordinary heat is generated due to some reason,resistive value of the thermosensitive organic material 13 filledbetween the heat generating member 2 and electrodes 11 will be loweredand, thus, a leakage current will flow through the filler 13 to any ofthe electrodes 11, so that the protecting device will be actuated so asto open the switch 14, thereby power supply to the heat generatingmember 2 will be interrupted.

Since in the thermosensitive electric surface heater as shown in theabove embodiment the heat generating member 2 and electrodes 11 arearranged with a certain space between them on the heatproof andinsulative film l in a plane form and the thermosensitive organicmaterial having a negative temperature resistive coefficient is filledin the space between the member 2 and electrodes 11, the heater willnever cause any inconveniences in using the same as any of thin typefioor heater or roof heater.

Turning next to FIGS. 4A and 4B the structure of another embodiment ofthe invention will be disclosed, in which I is the heatproof andinsulative plastic film, 2 is the electrically heat generating memberand I1 is the electrode plate. The heat generating member 2 and aplurality of the electrode plate 11 are arranged as shown in FIG. 3A soas to enter into each other but as spaced with a certain fixed distance.13 is a film of such thermosensitive organic material as polyethylene,polyamide or the like, 13' is a melted resin layer of likewise thepolyethylene, polyamide or the like, and said thermosensitive film 13 isadhered to the heat generating member 2 and electrode plates 11 with thelayer 13' as a binding agent. 18 is a metallic layer formed on the othersurface of said film 13 by way of vacuum evaporation, and is coveredwith a further heatproof insulating film 3.

The surface heater having the structure as above will be interconnectedso as to form such circuits as shown in FIGS. 4C and 4D for the purposeof practical use. In the drawings, 14 is a switch, 15 and 15 are powersources, 16 is a protective device, and 20 is a diode. In these wirings,if an extraordinary temperature rise is cause to occur at the point X,electric resistivity of the thermosensitive organic film 13 will belowered and, thus, a leakage current will be caused to flow to theprotective device 16 so as to open the switch 14.

In the surface heater of the above structure, a controlling voltage isimpressed to the metallic layer 18 and, therefore, respective electrodeplates II and metallic layer 18 will have the same potential at anyplace so that there exists the same electric voltage at any portion ofthem with respect to each other. This is effective in enabling theheater circuit to have the'same sensitivity and, thus, to detect anyabnormal condition at any place with a uniform sensitivity. Further, itis made possible to provide the heater which is highly flexible and isadapted to be manufactured in a continuous manner, since the same isformed of a synthetic resin and a metallic foil or vacuum evaporatedmetallic layer.

FIG. 5A shows a further embodiment of the invention, in which 21 is athermofusing resin layer adhered to a surface of a saturated polyesterfilm 22. 2 is a heat generating member, which is formed by adhering ametallic foil to inner surface of the saturated polyester film 22through any of thermoplastic resin such as polyethylene, nylon or thelike, polyurethane adhesive, rubber series adhesives and the like, andefi'ecting the etching process with respect to the foil so as to removeunnecessary portions therefrom. To the other exposed surface of thusformed heat generating member 2, a further saturated polyester film 22and a further thermofusing resin layer 21 will be adhered.

Connecting method of the surface heater having the above structure topower supplying lead wires shall be explained with reference to FIGS. 5Aand 53. Prior to the connection, the thermofusing resin layer 21 andsaturated polyester film 22 are partly removed from one of the bothsides of the heater so as to expose the heat generating member 2, and apower supplying lead wire 23 is then connected to said exposed portionof the member 2. Then, the lead wire 2 will be rolled up with thesaturated polyester film 22. Consequently the thermofusing resin layer21 adhered behind the film 22 will be exposed around the roll.

Thus rolled up saturated polyester film 22 having the lead wire 23inside will then be inserted into a sealing tube 24 for the connectingpart having a thermofusing resin layer 21 at its inner wall and,thereafter, the tube 24 will be heated under a pressure from outside,thereby the thermofusing resin layers 21 at both of the inner wall ofthe tube 24 and the outside surface of the rolled up polyester film 22will be jointed to each other so that a complete sealing of theconnection part may be established. It will be readily understood thatthe above connecting method is applicable to any embodiments asillustrated in FIGS. 3 and 4.

FIG. 6A shows a further embodiment of the present invention, in which 1is an insulative film, 2 is a plurality'of linear heat generating memberinterconnected to each other at an end, 4 is an adhesive layer ofthermoplastic resin, and 25 is a transparent sheet of plastics or glass.This embodiment is an example of the heater, on the whole surface ofwhich a design is formed by means of the heat generating member 2. Inorder to form this design, width of the respective linear members 2 andhence the space between each adjacent one of the members 2 will bevaried, so that sequential pattern of thus varied width of the'members 2will form any of the design or letter. In the case when the heatgenerating member is formed to designate, for example, a picturesquedesign, it is possible to obtain a surface heater having a decorativelydesigned metal sheet for use of setting on floor surfaces or adhering towall surfaces. Further in case the member is designating letters, itwill be possible to provide such heater that designates itself themanufactures identification or manufacturing numbers and so on, withoutneeding of such conventional labels to be adhered to the productionsthat will often be stripped off after a long use.

FIG. 6B is to show another embodiment, in which case a certain number ofdots or lines respectively arranged so as to represent as a whole any ofletters or designs. In the drawing, 1 is an insulative film, 2 is a heatgenerating member in a zigzag form, and 26 is a designation formed ofdots or lines which are respectively formed on the insulative film 1between each turn of the heat generating member 2. It will be preferableto utilize the same material for the dots or lines of the designationwith the one used for the heat generating member.

It will be also understood that the embodiments as disclosed withreference to FIGS. 6A and 68 will be readily applicable to theembodiments of FIGS. 3 and 4.

A still further embodiment of the invention is shown in FIG.

7, in which 1 is an insulative film and 2 is a heat generating member.Said member 2 is provided with a wider width part B at the periphery anda narrower width part C at the central section, so that the resistanceof the member 2 per a unit of area will be varied and, thus, the heatdistribution as generated with the resistance will be varied. By varyingthus the amount ofheat generated at each unit area, it is possible toproduce various types of the electric surface heater in response tovarious usages. In the case, for example, of using the surface heater byinstalling against interior wall of houses, the portion of such surfaceheater to be located at lower part of the wall may be adapted to producea larger amount of heat so that such defect that hot air tends to goupward and lower space becomes colder will be effectively prevented.

FIGS. 8A and 8B are to show a further embodiment of the invention, whichis adapted to make insulation work for peripheral part of the electricsurface heater according to the invention more simply carried out. Inthe drawings, 1 is a heatproof and insulative film, 2 is a linear heatgenerating member, and 27 is a lead conductor circuit. Said heatgenerating member 2 will be arranged and connected between two leadconductor circuits 27 arranged so as to be parallel to each other, sothat a block 28 will be formed. In order to carry out the electricinsulation at peripheral edge of the above structure when the surfaceheater is out along the chain line 29 in FIG. 8A, the cut edge part willbe folded down in the longitudinal direction of the heater as shown inFIG. 88, then the folded edge will be processed by means of anultrasonic or high frequency welding so that the folded films I and 3will be fused to each other and thus fixed firmly.

What we claim is:

I. A flexible, crack resistant electric surface heater comprising thecombination of a metal foil heat generating element, terminals forconnecting said heat generating element to an electrical source ofenergy at least two insulating plastic films disposed on opposite sidesof and surrounding said heat generating element, said heat generatingelement being continuously bonded to said insulating elements by anadhesive bonding agent, said heating element is formed in a zigzagpattern and said bonding agent is a thermoplastic resin which isutilized as a filler element to completely surround said heat generatingelement, completely filling the empty spaces created by said heatgenerating element being formed in a zigzag pattern, and completelyfilling any cavities existing in the surface of said heating element sothat there-are substantially no voids or airspaces within the enclosurecreated by said insulating elements and said metal foil heat generatingelement

1. A flexible, crack resistant electric surface heater comprising thecombination of a metal foil heat generating element, terminals forconnecting said heat generating element to an electrical source ofenergy at least two insulating plastic films disposed on opposite sidesof and surrounding said heat generating element, said heat generatingelement being continuously bonded to said insulating elements by anadhesive bonding agent, said heating element is formed in a zigzagpattern and said bonding agent is a thermoplastic resin which isutilized as a filler element to completely surround said heat generatingelement, completely filling the empty spaces created by said heatgenerating element being formed in a zigzag pattern, and completelyfilling any cavities existing in the surface of said heating element sothat there are substantially no voids or airspaces within the enclosurecreated by said insulating elements and said metal foil heat generatingelement and said plastic insulating elements being constructed ofmaterials having substantially identical thermal coefficients ofexpansion, said thermal coefficients of expansion are within the rangeof 2.0 X 10/* C. to 4.0 X 10/* C.